index

Gathering geospatial data

Both the neighborhood geometry and park geometry can be downloaded from Seattle GeoData:

I’ve saved a snapshot in the data directory.

The data format is gzipped GeoJSON. Java has a built-in class for handling gzip streams, and we’ll use the factual/geojson library to parse the string representation.

(defn slurp-gzip
  "Read a gzipped file into a string"
  [path]
  (with-open [in (java.util.zip.GZIPInputStream. (clojure.java.io/input-stream path))]
    (slurp in)))

Now we can conveniently load the data files we downloaded previously.

(defonce neighborhoods-geojson
  (slurp-gzip "data/Seattle/Neighborhood_Map_Atlas_Neighborhoods.geojson.gz"))

(def neighborhoods-features
  (geoio/read-geojson neighborhoods-geojson))

Let’s check that we got some data.

(count neighborhoods-features)

This seems like a reasonable number of neighborhoods. Each member of the dataset is called a Feature. Here is one:

(-> neighborhoods-features
    first
    kind/pprint)

{:properties
 {:OBJECTID 27,
  :L_HOOD "Ballard",
  :S_HOOD "Loyal Heights",
  :S_HOOD_ALT_NAMES nil,
  :Shape__Area 2.13206555455933E7,
  :Shape__Length 18831.00959637},
 :geometry
 #object[org.locationtech.jts.geom.Polygon 0x62f8f0a5 "POLYGON ((-122.376336564723 47.6759176989664, -122.376707907517 47.6759982290459, -122.377903057631 47.6759978849021, -122.379988625303 47.6759893429385, -122.38182788443 47.675992079457, -122.383602752477 47.675979810424, -122.385435721425 47.6759587956618, -122.387087434206 47.6759521343769, -122.387702391216 47.6759476875929, -122.388955759168 47.6759424488678, -122.390449346263 47.6759259868868, -122.391773109273 47.6759158131504, -122.392827172066 47.6759153143353, -122.392956550545 47.6759141859541, -122.392956303464 47.6763287099834, -122.392959618409 47.676929558447, -122.392961263359 47.6775085790216, -122.392971502986 47.6781034200237, -122.392975009807 47.6792517755972, -122.392983771129 47.6798142464259, -122.39300195772 47.6811303942788, -122.393014530791 47.6824285808909, -122.393016158048 47.6837341155494, -122.393022827056 47.685021586284, -122.393030577589 47.6863450742964, -122.393032746621 47.687668638629, -122.393046187318 47.6889956475812, -122.393010665051 47.6902980913372, -122.393002415356 47.6905813205566, -122.392432373275 47.6905826938111, -122.390347910813 47.6905631204492, -122.388192979124 47.6905805029145, -122.385832831602 47.6905766041982, -122.383275316007 47.690593164597, -122.383201215024 47.6905936585447, -122.381453020656 47.6905978829044, -122.379876313408 47.6905988541749, -122.379103841332 47.6906041929746, -122.377117910432 47.6906029639028, -122.376810344766 47.6906051591463, -122.376810264834 47.6905341242701, -122.376810989127 47.6900117143006, -122.376803067488 47.688976146724, -122.376794751014 47.6879443550321, -122.376800402808 47.6870068457338, -122.376784403749 47.6860923366759, -122.376785260609 47.6851813698577, -122.376780535885 47.6842704786057, -122.376787310842 47.6833707854178, -122.376777423242 47.6822860591882, -122.376767820487 47.6811938310584, -122.376770442503 47.680154307228, -122.376770065639 47.6792017979916, -122.376769882216 47.6780678404081, -122.376759750881 47.6775387646826, -122.376761985459 47.676862137338, -122.376772171763 47.6764361697665, -122.376772451106 47.6764114022001, -122.376770700102 47.6763866189683, -122.37676692258 47.6763619488292, -122.376761120573 47.6763374777451, -122.376753802121 47.6763131984825, -122.376744969247 47.6762891966531, -122.376733608705 47.6762655291531, -122.376721246367 47.6762423037704, -122.376706358898 47.6762194979699, -122.376690473449 47.6761972626929, -122.376672575492 47.6761756116819, -122.376653693551 47.6761550023704, -122.376620811506 47.6761243856628, -122.37659791092 47.6761051588887, -122.376573006221 47.6760868163511, -122.376547112434 47.6760693435982, -122.376519722058 47.6760527482053, -122.376336564723 47.6759176989664))"]}

Each feature, in our case, represents a geographic region with a geometry and some properties.

And similarly for the parks:

(defonce parks-geojson
  (slurp-gzip "data/Seattle/Park_Boundary_(details).geojson.gz"))

(def parks-features
  (geoio/read-geojson parks-geojson))

(count parks-features)

There are more parks than neighborhoods, which sounds right.

(delay
  (-> parks-features
      first
      kind/pprint))

{:properties
 {:SE_ANNO_CAD_DATA "",
  :NAMEFLAG 9,
  :ADDRESS " ",
  :MAINT "DPR",
  :LEASE "N",
  :PMA_NAME "East Duwamish GS: S Chicago St",
  :SUBPARCEL 9851,
  :PMA 442,
  :REVIEW_DATE "2004-04-08T00:00:00Z",
  :GlobalID "{D4B7025E-1135-4232-88AB-CBF72932E6AE}",
  :OBJECTID 207882,
  :AMWOID "PROPERTY-EDUWSC",
  :SDQL "QL-D1",
  :USE_ nil,
  :PIN "4006000485",
  :GIS_EDT_DT "2024-01-19T14:07:23Z",
  :SHAPE_Area 1.4691943312522366E-6,
  :SHAPE_Length 0.005215887160444538,
  :GIS_CRT_DT "2024-01-19T14:07:23Z",
  :NAME "EAST DUWAMISH GREENBELT",
  :OWNER "DPR",
  :ACQ_DATE "1997-10-21T00:00:00Z"},
 :geometry
 #object[org.locationtech.jts.geom.MultiPolygon 0x34f6e6a6 "MULTIPOLYGON (((-122.28235899499998 47.525165833000074, -122.28168484899999 47.525164389000054, -122.28168307199996 47.52516438600003, -122.28145050399996 47.52516388600003, -122.281450582 47.525147437000044, -122.28092621899998 47.525146310000025, -122.28092721899998 47.52433074500004, -122.28129411599997 47.52433142700005, -122.28247185299995 47.52433360800006, -122.28270306299999 47.52433403400005, -122.28270162899997 47.52516656600005, -122.28235899499998 47.525165833000074)))"]}

And the parks are defined as geographic regions.

Drawing a map

Seattle coordinates

(def Seattle-center
  [47.608013 -122.335167])

The map we will create is A choropleth, though for now, we will use a fixed color, which is not so informative.

We will enrich every feature (e.g., neighborhood) with data relevant for its visual representation.

(defn enrich-feature [{:as   feature :keys [geometry]}
                      {:keys [tooltip-keys
                              style]}]
  (-> feature
      (update :properties
              (fn [properties]
                (-> properties
                    (assoc :tooltip (-> properties
                                        (select-keys tooltip-keys)
                                        (->> (map (fn [[k v]]
                                                    [:p [:b k] ":  " v]))
                                             (into [:div]))
                                        hiccup/html)
                           :style style))))))

(def neighborhoods-enriched-features
  (-> neighborhoods-geojson
      (charred/read-json {:key-fn keyword})
      :features
      (->> (mapv (fn [feature]
                   (-> feature
                       (enrich-feature
                        {:tooltip-keys [:L_HOOD]
                         :style {:opacity     0.3
                                 :fillOpacity 0.1
                                 :color      "purple"
                                 :fillColor  "purple"}})))))))

We will need a tile layer for our visual map:

(def openstreetmap-tile-layer
  {:url         "https://tile.openstreetmap.org/{z}/{x}/{y}.png"
   :max-zoom    19
   :attribution "&copy;; <a href=\"http://www.openstreetmap.org/copyright\">OpenStreetMap</a>"})

Here is how we may generate a Choroplet map in Leaflet:

(defn choropleth-map [details]
  (delay
    (kind/reagent
     ['(fn [{:keys [tile-layer
                    center
                    enriched-features]}]
         [:div
          {:style {:height "900px"}
           :ref   (fn [el]
                    (let [m (-> js/L
                                (.map el)
                                (.setView (clj->js center)
                                          11))]
                      (let [{:keys [url max-zoom attribution]}
                            tile-layer]
                        (-> js/L
                            (.tileLayer url
                                        (clj->js
                                         {:maxZoom     max-zoom
                                          :attribution attribution}))
                            (.addTo m)))
                      (-> js/L
                          (.geoJson (clj->js enriched-features)
                                    (clj->js {:style (fn [feature]
                                                       (-> feature
                                                           .-properties
                                                           .-style))}))
                          (.bindTooltip (fn [layer]
                                          (-> layer
                                              .-feature
                                              .-properties
                                              .-tooltip)))
                          (.addTo m))
                      #_(->> enriched-features
                             (run! (fn [{:keys [properties geometry]}]
                                     (let [{:keys [style tooltip]} properties]
                                       (case (:type geometry)
                                         "Polygon" (-> js/L
                                                       (.polygon (-> geometry
                                                                     :coordinates
                                                                     first
                                                                     clj->js)
                                                                 (-> style
                                                                     (or {})
                                                                     clj->js (or style {})))
                                                       (.bindTooltip tooltip)
                                                       (.addTo m))
                                         "MultiPolygon" (-> js/L
                                                            (.multiPolygon (-> geometry
                                                                               :coordinates
                                                                               clj->js)
                                                                           (-> style
                                                                               (or {})
                                                                               clj->js (or style {})))
                                                            (.bindTooltip tooltip)
                                                            (.addTo m))
                                         ;; else
                                         (-> geometry
                                             :type
                                             (str " - unrecognized geometry type")
                                             js/alert))))))))}])
      details]
     {:reagent/deps [:leaflet]})))

For our basic neighborhoods map:

(delay
  (choropleth-map
   {:tile-layer openstreetmap-tile-layer
    :center     Seattle-center
    :enriched-features neighborhoods-enriched-features}))

Now, let us see the parks:

(def parks-enriched-features
  (-> parks-geojson
      (charred/read-json {:key-fn keyword})
      :features
      (->> (mapv (fn [feature]
                   (-> feature
                       (enrich-feature
                        {:tooltip-keys [:PMA_NAME :NAME]
                         :style {:opacity     0.3
                                 :fillOpacity 0.1
                                 :color      "darkgreen"
                                 :fillColor  "darkgreen"}})))))))

(delay
  (choropleth-map
   {:tile-layer openstreetmap-tile-layer
    :center     Seattle-center
    :enriched-features parks-enriched-features}))

Coordinate conversions

Both datasets use the WGS84 coordinate system.

EPSG:4326

For area computations we need to convert them to a coordinate system which is locally correct in terms of distances in a region around Seattle.

EPSG:2285

United States (USA) - Oregon and Washington. [1 3]:

Center coordinates	Projected bounds	WGS84 bounds
[1692592.39 -541752.55]	[[559165.71 -1834123.81] [2832684.98 777497.1]]	[[-124.79 41.98] [-116.47 49.05]]

(def crs-transform
  (geo.crs/create-transform (geo.crs/create-crs 4326)
                            (geo.crs/create-crs 2285)))

(defn wgs84->Seattle
  "Transforming latitude-longitude coordinates
  to local Euclidean coordinates around Seattle."
  [geometry]
  (geo.jts/transform-geom geometry crs-transform))

Some geometrical functions

(defn area [geometry]
  (.getArea geometry))

(defn buffer [geometry radius]
  (.buffer geometry radius))

(defn intersection [geometry1 geometry2]
  (.intersection geometry1 geometry2))

Geometry datasets

(defn geojson->dataset [geojson dataset-name]
  (-> geojson
      (->> (map (fn [{:keys [geometry properties]}]
                  (assoc properties :geometry geometry))))
      tc/dataset
      (tc/map-columns :geometry [:geometry] wgs84->Seattle)
      (tc/set-dataset-name dataset-name)))

(def neighborhoods
  (-> neighborhoods-features
      (geojson->dataset "Seattle neighborhoods")))

(delay
  (-> neighborhoods
      (tc/drop-columns [:geometry])
      kind/table))

OBJECTID	L_HOOD	S_HOOD	S_HOOD_ALT_NAMES	Shape__Area	Shape__Length
27	Ballard	Loyal Heights		2.13206555455933E7	18831.00959637
28	Ballard	Ballard	Adams	2.25521329700012E7	29926.3393002841
29	Ballard	Whittier Heights		1.41956874919434E7	15934.4392663199
30	Ballard	West Woodland		2.21993668730164E7	21789.6510873493
31	North Central	Phinney Ridge	Woodland Park	3.21231178777466E7	27120.7859379681
32	North Central	Wallingford	Meridian, Tangle Town, Northlake	4.20683426137695E7	33040.2469861198
33	North Central	Fremont		2.65037565718689E7	25999.2849357187
34	North Central	Green Lake		3.73146297898865E7	25387.7074962486
35	Northeast	View Ridge		2.56129799440918E7	22657.0394732799
36	Northeast	Ravenna	University Village	3.67833915366516E7	31163.6208763331
37	Northeast	Sand Point		1.92498571397095E7	21396.6958008648
38	Northeast	Bryant		1.54850780333252E7	20928.0017243062
39	Northeast	Windermere	Hawthorne Hills	2.23639666230164E7	33332.8291968304
40	Northeast	Laurelhurst		1.90517768183594E7	26489.2422321737
41	Northeast	Roosevelt	Fairview	2.1491594324707E7	22866.0797374364
42	University District	University of Washington		2.55236751180115E7	30983.2126641678
43	Queen Anne	East Queen Anne		1.93546995965576E7	21488.397378299
44	Queen Anne	West Queen Anne		1.79749859528503E7	20631.7057292923
45	Queen Anne	Lower Queen Anne	Uptown, Seattle Center	1.75156244566956E7	20496.7289222394
46	Queen Anne	North Queen Anne		2.9604288333252E7	26753.5542817429
47	Cascade	Westlake		3645184.07894897	11017.3231739615
48	Cascade	Eastlake		7426907.96139526	16672.5117837403
49	Cascade	South Lake Union		1.6107105419342E7	29323.5462843847
50	Magnolia	Lawton Park		5.5091525290863E7	38766.0673349107
51	Magnolia	Briarcliff	Carleton Park	2.65509365782471E7	26609.7912261135
52	Magnolia	Southeast Magnolia		1.84692638882751E7	20223.1801501522
53	Central Area	Madrona		1.38454828085938E7	17052.9427067693
54	Central Area	Harrison/Denny-Blaine		1.36033956731873E7	17241.2743191595
55	Central Area	Minor	Central District, Squire Park	1.7933144708252E7	18241.5487859812
56	Central Area	Leschi		1.80917413764954E7	20413.0560516882
57	Central Area	Mann	Central District, Garfield	1.11338288620605E7	17843.105758736
58	Central Area	Atlantic	Judkins Park, Jackson Place, Coleman	2.06649862726135E7	25426.2311626675
59	Downtown	Pike-Market	Pike Place Market	2343359.32580566	7326.58173024624
60	Downtown	Belltown	Denny Regrade	9845864.78594971	17836.7271544608
61	Downtown	International District	Chinatown, ID, Little Saigon	6169375.81655884	11772.3871410021
62	Downtown	Central Business District	Commercial Core, West Edge	9477398.61834717	18209.4628624588
63	Downtown	First Hill		9517568.47363281	13225.2335159542
64	Downtown	Yesler Terrace		5348937.24771118	9611.35354641661
65	Downtown	Pioneer Square		7545979.0869751	17297.5867148564
66	Interbay	Interbay		3.35039410921631E7	64207.5867611718
67	Greater Duwamish	SODO		4.96031675905914E7	38520.9885110863
68	Greater Duwamish	Georgetown		5.13050726461182E7	45963.6656769607
69	Greater Duwamish	South Park		2.94234521522369E7	30433.4048686311
70	Greater Duwamish	Harbor Island		1.78323007354431E7	24381.2966280601
71	West Seattle	Seaview		1.8463061797821E7	23122.2640032568
72	West Seattle	Gatewood	Morgan Junction	2.28217074689484E7	23801.2647005122
73	West Seattle	Arbor Heights		2.61973140573883E7	28162.4351386166
74	West Seattle	Alki		2.45834691841736E7	45568.1378536906
75	West Seattle	North Admiral	Belvidere	4.85814163202972E7	30687.7844700837
76	West Seattle	Fairmount Park		1.61539000976257E7	24955.7128414259
77	West Seattle	Genesee	Alaska Junction, West Seattle Junction	2.11649765813446E7	19870.8696089241
78	West Seattle	Fauntleroy	Endolyne, Arroyo Heights, Brace Point	3.38818638706665E7	42276.5317877774
79	Beacon Hill	North Beacon Hill	Jefferson Park	4.84759144557953E7	33865.4891739901
80	Beacon Hill	Mid-Beacon Hill		5.26204707883301E7	40522.1829275323
81	Beacon Hill	South Beacon Hill		3.84488268989563E7	38996.7151070849
82	Beacon Hill	Holly Park	New Holly	8444235.97859192	15848.3624185113
83	Rainier Valley	Brighton		1.8366938275177E7	18911.3293490837
84	Rainier Valley	Dunlap		1.96016012150879E7	20847.6531922997
85	Rainier Valley	Rainier Beach		3.31282361414948E7	34965.6132100475
86	Rainier Valley	Rainier View	Lake Ridge	1.82485661794434E7	34791.8218147105
87	Rainier Valley	Mount Baker	North Rainier	2.89869952343292E7	26318.9819054871
88	Rainier Valley	Columbia City	Columbia Heights	3.74065764927979E7	35177.0608039675
89	Delridge	Highland Park		3.98103334158325E7	31111.0630837714
90	Delridge	North Delridge	Avalon, Luna Park, Pigeon Point	2.94546565672607E7	23549.9313666304
91	Delridge	Riverview		3.30382671929626E7	25917.1176391015
92	Delridge	High Point		2.33430083368683E7	23180.3963596714
93	Delridge	South Delridge	White Center	1.79233162238464E7	23416.3405359794
94	Delridge	Roxhill	Westwood Village	1.87810598441162E7	22360.0472289145
95	Seward Park	Seward Park	Lakewood, Hillman City	4.38352790059662E7	52212.7868103531
96	Northeast	Wedgwood		3.05997136261597E7	23840.2187274324
97	Capitol Hill	Portage Bay	Roanoke Park	4421635.26721191	10013.2739563989
98	Capitol Hill	Montlake	North Capitol Hill	2.1474786741394E7	46165.83098345
99	Capitol Hill	Madison Park	Broadmoor, Washington Park	2.46809502223511E7	26230.4347480002
100	Capitol Hill	Broadway	Pike/Pine	3.02392405212402E7	26851.9474418256
101	Capitol Hill	Stevens	Interlaken Park, Miller Park, Madison-Miller	2.60395920790405E7	25522.3456368768
102	Lake City	Victory Heights		2.15127314890137E7	20753.0018992847
103	Lake City	Matthews Beach		3.09809783014832E7	31369.8925404597
104	Lake City	Meadowbrook		1.70348487789307E7	18770.2820324215
105	Lake City	Olympic Hills		2.58367421641541E7	19993.8160570763
106	Lake City	Cedar Park		2.04414858487244E7	22788.760382662
110	Northwest	Broadview		4.81134497303162E7	34640.309665739
111	Northwest	Bitter Lake		2.76903364438171E7	26446.2030540938
112	Northgate	Haller Lake		4.72030810796204E7	29413.5534484151
113	Northgate	Pinehurst	Jackson Park	2.94388508770142E7	26171.2717608103
114	Northwest	North Beach/Blue Ridge		3.10622649915771E7	32947.8059119899
115	Northgate	Licton Springs	North College Park	2.17047062611389E7	20132.8982458333
116	Northgate	Maple Leaf	Olympic View	3.43804707826233E7	25503.0574082691
117	Northwest	Crown Hill		1.58657504196777E7	18997.8080379411
118	Northwest	Greenwood		4.20445636731262E7	26501.5265911049
119	Ballard	Sunset Hill	Golden Gardens, Shilshole	2.43356204689941E7	29416.7300633571
121	University District	University District		1.36862548569946E7	21581.6459789299
123	University District	University Heights	Cowen Park	1.03757480522461E7	15163.9069096811
124	Downtown	Denny Triangle	Denny Regrade	5128172.31045532	10574.1779826691
126	Greater Duwamish	Industrial District		6.24341310114746E7	88995.7569839975

(def parks
  (-> parks-features
      (geojson->dataset "Seattle parks")
      ;; avoiding some [linestring pathologies](https://gis.stackexchange.com/questions/50399/fixing-non-noded-intersection-problem-using-postgis)
      (tc/map-columns :geometry [:geometry] #(buffer % 1))))

(delay
  (-> parks
      (tc/drop-columns [:geometry])
      (tc/head 20)
      kind/table))

NAMEFLAG	ADDRESS	MAINT	LEASE	PMA_NAME	SUBPARCEL	PMA	REVIEW_DATE	GlobalID	OBJECTID	AMWOID	SDQL	PIN	GIS_EDT_DT	SHAPE_Area	SHAPE_Length	GIS_CRT_DT	NAME	OWNER	ACQ_DATE
9		DPR	N	East Duwamish GS: S Chicago St	9851	442	2004-04-08T00:00:00Z	{D4B7025E-1135-4232-88AB-CBF72932E6AE}	207882	PROPERTY-EDUWSC	QL-D1	4006000485	2024-01-19T14:07:23Z	1.4691943312522366E-6	0.005215887160444538	2024-01-19T14:07:23Z	EAST DUWAMISH GREENBELT	DPR	1997-10-21T00:00:00Z
9		DPR	N	East Duwamish GS: S Chicago St	4779	443	2004-04-08T00:00:00Z	{26B4F4BC-F9AE-42D4-B062-51387C6D9FFF}	207883	PROPERTY-EDUWC	QL-D1	0603001220	2024-01-19T14:07:23Z	1.460570191594512E-7	0.0015461198840460832	2024-01-19T14:07:23Z	EAST DUWAMISH GREENBELT	DPR	1994-10-06T00:00:00Z
9		DPR	N	East Duwamish GS: S Chicago St	4711	443	2004-04-08T00:00:00Z	{E97D7F7F-2666-4008-A905-2F416A66C2A1}	207884	PROPERTY-EDUWC	QL-D1	0603001220	2024-01-19T14:07:23Z	9.743577447048599E-8	0.0013271653095071236	2024-01-19T14:07:23Z	EAST DUWAMISH GREENBELT	DPR	1994-10-06T00:00:00Z
9		DPR	N	East Duwamish GS: S Chicago St	4779	443	2004-04-08T00:00:00Z	{C28A4700-BB4F-4C25-928E-57022F6D001B}	207885	PROPERTY-EDUWC	QL-D1	0603001220	2024-01-19T14:07:23Z	4.87386722719263E-8	0.0011082207640129814	2024-01-19T14:07:23Z	EAST DUWAMISH GREENBELT	DPR	1994-10-06T00:00:00Z
9		DPR	N	East Duwamish GS: S Chicago St	4712	443	2004-04-08T00:00:00Z	{4DB6A932-327A-4E2E-AC8A-C068D114AA61}	207886	PROPERTY-EDUWC	QL-D1	0603001220	2024-01-19T14:07:23Z	9.757207624044397E-8	0.0013284113092379031	2024-01-19T14:07:23Z	EAST DUWAMISH GREENBELT	DPR	1994-10-06T00:00:00Z
9		DPR	N	Genesee Park and Playfield	4618	409	1899-12-30T00:00:01Z	{AD2E47C9-323B-4DDE-8186-98A4FC79C3F8}	207887	PROPERTY-GENPK	QL-D1	4154300585	2024-01-19T14:07:23Z	2.892289652506793E-6	0.007000440212562059	2024-01-19T14:07:23Z	GENESEE PARK AND PLAYFIELD	DPR	1996-06-03T00:00:00Z
9	5244 SW JACOBSEN ROAD	DPR	N	Wolf Creek Ravine Natural Area	16397	278	2004-04-19T00:00:00Z	{A7E54352-0DC3-47E4-B562-DAA0F18B78E2}	207888	PROPERTY-WLFCRAV	QL-D1	5344200125	2024-01-19T14:07:23Z	6.25557675764001E-8	0.0010504796990982068	2024-01-19T14:07:23Z	WOLF CREEK RAVINE NATURAL AREA	DPR	2004-04-07T00:00:00Z
9		DPR	N	Jefferson Park	15550	114	2004-04-08T00:00:00Z	{B82B7BD2-DCD9-49A2-BE5D-30C1D9BF4392}	207889	PROPERTY-JEFFPK	QL-D1	1624049270	2024-01-19T14:07:23Z	3.2670040661028276E-6	0.018380332716286137	2024-01-19T14:07:23Z	JEFFERSON PARK	DPR	1988-07-25T00:00:00Z
9		DPR	N	Queen Anne Boulevard	753	328	2004-04-09T00:00:00Z	{3DA31C7B-C33D-4DD9-9092-71B1DA135BC8}	207890	PROPERTY-QABL	QL-D1	2533300180	2024-01-19T14:07:23Z	5.790553187521671E-9	4.111515370853996E-4	2024-01-19T14:07:23Z	QUEEN ANNE BOULEVARD	DPR	1910-07-25T00:00:01Z
9		DPR	N	Queen Anne Boulevard	4688	328	2004-04-09T00:00:00Z	{D3DA12EE-31E0-4476-95CE-1739E8FF8550}	207891	PROPERTY-QABL	QL-D1	2533300180	2024-01-19T14:07:23Z	5.139665582905777E-9	3.9228813174494234E-4	2024-01-19T14:07:23Z	QUEEN ANNE BOULEVARD	DPR	1910-07-25T00:00:01Z
7		DPR	N	Ravenna Woods	15807	4411	2004-05-05T00:00:00Z	{B1A2F3C6-C43A-4600-8064-A3DEFAE61DDC}	207892	PROPERTY-RAVWOOD	QL-D1	0925049168	2024-01-19T14:07:23Z	5.585829095854119E-7	0.0030915009702507513	2024-01-19T14:07:23Z	RAVENNA WOODS	DPR	2002-07-02T00:00:00Z
9		DPR	N	Montlake Playfield	1507	376	1998-10-15T00:00:00Z	{BF38EE1A-DBAB-400C-B083-B3F8B6A1EB39}	207893	PROPERTY-MTLKPF	QL-D1	4089400080	2024-01-19T14:07:23Z	3.917576385699785E-7	0.0026768636765498316	2024-01-19T14:07:23Z	MONTLAKE PLAYFIELD	DPR	1933-12-31T00:00:01Z
9		DPR	N	Montlake Playfield	1507	376	2004-03-30T00:00:00Z	{4CC47610-4927-465F-A346-04F66008D480}	207894	PROPERTY-MTLKPF	QL-D1	6788202280	2024-01-19T14:07:23Z	1.1273410584671711E-6	0.004459900867682873	2024-01-19T14:07:23Z	MONTLAKE PLAYFIELD	DPR	1933-12-31T00:00:01Z
9		DPR	N	Montlake Playfield	1507	376	2004-03-30T00:00:00Z	{10310B09-822A-4344-95CC-2D5D90C2466C}	207895	PROPERTY-MTLKPF	QL-D1	6788202280	2024-01-19T14:07:23Z	1.4591960880701082E-6	0.006312257575513224	2024-01-19T14:07:23Z	MONTLAKE PLAYFIELD	DPR	1933-12-31T00:00:01Z
9	4357 PALATINE AVE N	DPR	N	Fremont Peak Park	16454	4424	2004-10-06T00:00:00Z	{A13D75B6-B355-4BDF-84CF-4D2838170201}	207896	PROPERTY-FRMPKPK	QL-D1	6610000810	2024-01-19T14:07:23Z	6.118914081332531E-8	0.0011669443524576426	2024-01-19T14:07:23Z	FREMONT PEAK PARK	DPR	2004-09-30T00:00:00Z
9		DPR	N	SW Queen Anne Greenbelt	16459	234	2005-01-06T00:00:00Z	{A13C70F6-F0AE-4E55-A12C-990BBC545F8D}	207897	PROPERTY-SWQAGRB	QL-D1	7705100037	2024-01-19T14:07:23Z	5.565195258199712E-9	3.556012201607765E-4	2024-01-19T14:07:23Z	SW QUEEN ANNE GREENBELT	DPR	2004-11-04T00:00:00Z
3	9026 4TH AVE S	DPR	N	Marra-Desimone Park	16455	4447	2007-02-21T00:00:00Z	{E641A30D-FE4B-4B1D-9358-7F0F71324691}	207898	PROPERTY-MARDESPK	QL-D1	3224049044	2024-01-19T14:07:23Z	2.211413981358282E-6	0.006388002898489655	2024-01-19T14:07:23Z	MARRA-DESIMONE PARK	DPR	2004-12-28T00:00:00Z
9	9026 4TH AVE S	DPR	N	Marra-Desimone Park	16455	4447	2007-02-21T00:00:00Z	{6A440787-F078-4DB9-9187-DA0E029A8E18}	207899	PROPERTY-MARDESPK	QL-D1	3224049035	2024-01-19T14:07:23Z	1.981420659558925E-6	0.009774073825241834	2024-01-19T14:07:23Z	MARRA-DESIMONE PARK	DPR	2004-12-28T00:00:00Z
9		DPR	Y	Meadowbrook Playfield	803	352		{49C14F14-94FF-4080-9DE8-56EDF006145A}	207900	PROPERTY-MBPF	QL-D1		2024-01-19T14:07:23Z	5.268695375108406E-7	0.00550990095454217	2024-01-19T14:07:23Z	MEADOWBROOK PLAYFIELD	SSD1
9		DPR	N	Meadowbrook Teen Life Center		352		{D099D793-CFEA-44E9-A57B-D8A1BA4525AF}	207901	PROPERTY-MBPF	QL-D1		2024-01-19T14:07:23Z	8.504523207167994E-8	0.0011865488770908574	2024-01-19T14:07:23Z	MEADOWBROOK TEEN LIFE CENTER	SSD1

A Spatial index structure

We need an index structure to quickly match between the two sets of geometries.

See the JTS SearchUsingPreparedGeometryIndex tutorial.

(defn make-spatial-index [dataset & {:keys [geometry-column]
                                     :or   {geometry-column :geometry}}]
  (let [tree (org.locationtech.jts.index.strtree.STRtree.)]
    (doseq [row (tc/rows dataset :as-maps)]
      (let [geometry (row geometry-column)]
        (.insert tree
                 (.getEnvelopeInternal geometry)
                 (assoc row
                        :prepared-geometry
                        (org.locationtech.jts.geom.prep.PreparedGeometryFactory/prepare geometry)))))
    tree))

(def parks-index
  (make-spatial-index parks))

(defn intersecting-places [region spatial-index]
  (->> (.query spatial-index (.getEnvelopeInternal region))
       (filter (fn [row]
                 (.intersects (:prepared-geometry row) region)))
       tc/dataset))

For example, let us find the parks intersecting with the first neighborhood:

(delay
  (-> neighborhoods
      :geometry
      first
      (intersecting-places parks-index)
      (tc/select-columns [:PMA_NAME :NAME])))

_unnamed [2 2]:

:PMA_NAME	:NAME
Salmon Bay Park	SALMON BAY PARK
Loyal Heights Playfield	LOYAL HEIGHTS PLAYFIELD

A Joined dataset

We compute a spatial join of the two datasets.

Note that even though many parks will appear as intersecting many neighbourhoods, this is not too memory-heavy, since they are references to the same map.

(def neighborhoods-with-parks
  (-> neighborhoods
      (tc/map-columns :parks
                      [:geometry]
                      #(intersecting-places % parks-index))))

(delay
  (-> neighborhoods-with-parks
      (tc/map-columns :n-parks
                      [:parks]
                      tc/row-count)
      (tc/select-columns [:L_HOOD :n-parks])))

Seattle neighborhoods [94 2]:

:L_HOOD	:n-parks
Ballard	2
Ballard	7
Ballard	4
Ballard	5
North Central	11
North Central	27
North Central	15
North Central	19
Northeast	15
Northeast	12
…	…
Northgate	8
Northwest	32
Northgate	6
Northgate	18
Northwest	5
Northwest	36
Ballard	9
University District	11
University District	21
Downtown	3
Greater Duwamish	5

Computing areas

For every neighborhood, we will compute the proportion of its area covered by parks.

TODO: L_HOOD should be used, S_HOOD produces too many rows to be understood (maybe S_HOOD would be interesting for looking at one L_HOOD at a time)

(delay
  (-> neighborhoods-with-parks
      (tc/map-columns :neighborhood-area
                      [:geometry]
                      area)
      (tc/map-columns :intersection-area
                      [:geometry :parks]
                      (fn [neigh-geometry parks]
                        (->> parks
                             :geometry
                             (map (fn [park-geometry]
                                    (area
                                     (.intersection (.buffer park-geometry 1)
                                                    neigh-geometry))))
                             fun/sum)))
      (tc/map-columns :park-names
                      [:parks]
                      (fn [parks]
                        (->> parks
                             :PMA_NAME
                             distinct
                             vec)))
      (tc/add-column :area-proportion
                     #(fun// (:intersection-area %)
                             (:neighborhood-area %)))
      (tc/select-columns [:L_HOOD
                          :park-names
                          :neighborhood-area
                          :intersection-area
                          :area-proportion])
      (tc/order-by [:area-proportion] :desc)))

Seattle neighborhoods [94 5]:

:L_HOOD	:park-names	:neighborhood-area	:intersection-area	:area-proportion
Northeast	[Warren G. Magnuson Park]	1.92498571E+07	1.26944073E+07	0.65945463
Magnolia	[Magnolia Manor Park	5.50915253E+07	2.57689116E+07	0.46774729
	Lawton Park
	Discovery Park
	Kiwanis Memorial Preserve Park
	Discovery Park Boulevard
	Discovery Park Tidelands
	Kiwanis Ravine Overlook
	Daybreak Star
	Commodore Park]
Delridge	[Greg Davis Park	2.94546566E+07	1.32455699E+07	0.44969358
	Cottage Grove Park
	Rotary Viewpoint
	Camp Long
	West Seattle Golf Course
	West Seattle Stadium
	Longfellow Creek GS: North
	Puget Boulevard
	West Duwamish Greenbelt
	Pigeon Point
	Delridge Playfield
	Westbridge Shops
	WEST DUWAMISH GREENBELT]
North Central	[Ravenna Boulevard	3.73146298E+07	1.53146452E+07	0.41041932
	Green Lake Park
	Green Lake
	Crescent Place
	North Park Shops]
Seward Park	[Martha Washington Park	4.38352790E+07	1.32526645E+07	0.30232874
	Seward Park
	Lake Washington Boulevard
	Lakewood Playground
	Lakewood Moorage
	Genesee Park and Playfield
	Stan Sayres Memorial Park]
Delridge	[Delridge and Myrtle	3.30382672E+07	8.76957592E+06	0.26543692
	West Duwamish GS: Riverview
	Riverview Playfield
	West Duwamish GS: Puget Park
	Puget Creek Edible Park
	Puget Creek Greenspace
	Puget Ridge Playground
	Delridge Wetland
	Puget Park
	Puget Boulevard
	Pigeon Point]
North Central	[Cascade Place	3.21231179E+07	8.34975296E+06	0.25992972
	Sunset Place
	Rainier Place
	Woodland Park Zoo
	Woodland Park
	Linden Orchard Park
	Green Lake Park]
Northgate	[Hubbard Homestead Park	2.94388509E+07	7.64686119E+06	0.25975407
	Victory Creek Park
	Pinehurst Playground
	Flicker Haven Natural Area on Thornton Creek
	Licorice Fern Natural Area on Thornton Creek
	Jackson Park Golf Course]
Capitol Hill	[Washington Park and Arboretum	2.14747867E+07	5.45298611E+06	0.25392504
	Interlaken Park
	Montlake Boulevard
	Lake Washington Boulevard
	East Montlake Park
	Grand Army Cemetery
	Montlake Playfield
	Harvard-Miller/Roanoke Annex
	West Montlake Park]
West Seattle	[Fauntleroy Park	3.38818639E+07	7.39981718E+06	0.21840053
	Arroyos Natural Area
	Stim Bullitt Natural Area
	Endolyne Park
	Fauntleroy Creek Ravine
	Lincoln Park
	Kilbourne Park
	Solstice Park]
…	…	…	…	…
Delridge	[Longfellow Creek GS: South]	1.79233162E+07	1.32742172E+05	0.00740612
Queen Anne	[Blaine Place	1.75156245E+07	1.06952952E+05	0.00610615
	Counterbalance Park
	Kinnear Place
	Kerry Park (Franklin Place)
	Kerry Park and Viewpoint
	Ward Springs Park]
Northwest	[Crown Hill Glen Crown Hill Park]	1.58657504E+07	9.49434049E+04	0.00598417
University District	[Union Bay Boglands #2 Union Bay Boglands #1 Fritz Hedges Waterway Park]	2.55236751E+07	1.42125035E+05	0.00556836
Greater Duwamish	[Georgetown Pump Station Oxbow Park Georgetown Playfield]	5.13050726E+07	2.81438227E+05	0.00548558
Lake City	[Thornton Creek Addition: North Branch	2.58367422E+07	1.41195814E+05	0.00546492
	Albert Davis Park
	Little Brook Park]
West Seattle	[West Seattle Junction	2.11649766E+07	9.18911781E+04	0.00434166
	Junction Plaza Park
	Ercolini Park
	Dakota Place Park
	48th Ave SW/SW Charlestown St
	Fauntleroy Place]
West Seattle	[Lowman Beach Park Morgan Junction Park]	1.84630618E+07	5.18603372E+04	0.00280887
Downtown	[McGraw Square Westlake Square Urban Triangle Park]	5.12817231E+06	1.16681726E+04	0.00227531
Greater Duwamish	[]	1.78323007E+07	0.00000000E+00	0.00000000
Greater Duwamish	[]	4.96031676E+07	0.00000000E+00	0.00000000

TODO: The area proportions would be best represented in a bar chart to accompany the table TODO: summarizing the quartiles of values might be useful as well TODO: An interesting map would show just one L_HOOD and all the parks, perhaps choosing the “winner” with most park space and showing where in Seattle it is, and what parks are there.

Conclusion

Park access is fairly uniform and high in Seattle. TODO: can we compare it to another city?

source: projects/geography/seattle-parks/notebooks/index.clj

Seattle Parks & Neighborhoods